The present invention relates to a security lock for hinged doors and, more particularly, to a mechanism which both locks and reinforces a door.
Mechanisms presently available for locking a hinged door are usually sufficient to prevent casual or inadvertent opening of the door. Even locking mechanisms employed on exterior doors are hardly strong enough to resist a determined effort at entry. Consequently, various supplementary mechanisms, such as chains, dead bolts, etc., have been proposed to provide a security against unauthorized opening of a door. The degree of security offered by such mechanisms has often proved to be illusory, since either the mounting of the mechanism is inadequate or the door and/or the supporting frame are weakened by installation of the mechanism. With door chains and some bolts, a portion of the mechanism is often attached to the casing surrounding the door where it can be dislodged by a sudden blow. Other bolts are received in holes drilled in the frame or receptacles attached to the frame. In either case, where is essentially point contact between the bolt and the frame, such that force applied to the door is concentrated at a single point on the frame.
For ease of operation, it has been the practice to install the supplementary mechanisms in the immediate vicinity of the locking mechanism, i.e., approximately midlength of the swinging edge of the door. While the hinged edge is supported by the hinges at widely spaced locations near the top and bottom of the frame, the swinging edge is supported by the locking and supplementary mechanisms which are closely spaced and concentrated in one area of the frame. Thus, pressure applied at the swinging edge of the door is concentrated within a small area of the frame creating enormous forces which can splinter the frame and dislodge the various mechanisms.